'More smoke than fire'

"Solar's long-term prospects are much more powerful than one tariff decision," Ed Fenster, executive chairman of solar-energy leader Sunrun(RUN), told CNNMoney. "Solar's future is secure even in the face of temporary poor federal policy."

Many in the solar world were bracing for more punishing tariffs from Trump.

"It's a lot more smoke than fire," saidBryan Birsic, CEO of Wunder Capital, which develops and manages solar investments. Birsic is "excited" about where the tariffs landed compared with what he expected.

Utility company Duke Energy(DUKH) acknowledged that the solar panel tariffs will "hurt" its plan to nearly quadruple solar power capacity over the next five years.

However, Duke said it will "continue to invest in this resource" because "our customers expect solar to be a key component of an affordable and clean energy generation mix."

Renewables are getting cheaper

Simple economics has helped renewables take off. New technology, soaring investment dollars and government support have drastically lowered the cost of wind and solar, allowing them to be competitive with fossil fuels in some places.

The cost of solar electricity plummeted two-thirds between 2010 and 2017, according to the National Renewable Energy Laboratory.

The Energy Information Administration estimates that renewable energy now makes up about 17% of U.S. electricity generation, up from just 8% in 2001.

Coal's share of the electric grid plummeted to 30% last year, from more than half in 2001, according to the EIA. Much of that decline was driven by the abundance of cheap natural gas thanks to the shale revolution.

The EIA expects renewables and natural gas to steal more market share in the next two years, while coal is projected to decline further.

"The reality is that renewables are increasingly cost-effective," said PJ Deschenes, a partner atGreentech Capital Advisors, a clean energy investment bank.

Solar costs are expected to keep going down in the long run. The cost of solar electricity is poised to crater by 66% by 2040, according to a forecast last year by the research firm Bloomberg New Energy Finance. The report predicted U.S. power generation from renewable energy will skyrocket 169% in that time.

Bank of America Merrill Lynch expects clean energy will account for up to 80% of all the new power in the world through 2040.

Trump has repeatedly promised to resuscitate the coal industry. Last year, he moved to roll back Obama-era environmental rules, and Energy Secretary Rick Perry proposed a controversial plan to prop up slumping coal companies.

But the renewable industry dodged a bullet in January when the Federal Energy Regulatory Commission unanimously dismissed Perry's call to subsidize coal and nuclear power plants.

"The administration has shown blatant favoritism to traditional energy sources such as fossil fuels," said Tao Kong, chief operating officer at Alcen Renewable, which develops wind and solar projects for utilities.

Grassroots green support

The Trump administration has so far mostly avoided outright targeting renewables, which enjoy strong public support.